Transformation of Biomass and Shale Gas Carbon to Fuels and Chemicals

Taufik Ridha, Purdue University

Abstract

Currently, fossil resources dominate fuel and chemical production landscape. Besides concerns related to the ever-increasing greenhouse gas emission, fossil resources are also limited. In a petroleum-deprived future, sustainably available biomass can serve as a renewable carbon source. Due to its limited availability, however, this biomass resource must be utilized and converted efficiently to minimize carbon losses to undesirable by-products. A modeling and optimization approach that can identify optimal process configurations for chemical and fuel production from biomass using stoichiometric and thermodynamic knowledge of the underlying biomass reaction system is proposed in this dissertation. Several case studies were performed with this approach, and the outcomes found agreement with reported experimental results. In particular, a case study on fast-hydropyrolysis vapor of cellulose led to the discovery of new reaction route and provided insights in comprehending the formation of experimentally observed molecules. The modeling and optimization approach consists of two main steps. The first step is the generation of the search space and the second step is the identification of all optimal reaction routes. For the first step, literature review and automated reaction network generator are employed to identify all possible processes for biomass conversion. Through literature review, yield data on processes that generate biomass-derived molecules are collected. As these biomass-derived molecules often possess multiple functional groups, utilization of automated reaction network generator, which considers a set of biomass-derived molecules and reaction rules, enables generation of all possible reactions. In this work, an automated reaction network generator tool called Rule Input Network Generator is utilized. Using this generated search space, a mathematical optimization problem, which identifies the optimal reaction network, is constructed. For the second step, the optimization problem identifies all reaction routes with the minimum number of reactions for a given set of biomass and target products. This formulation constructs a process superstructure that contains processes that generate biomass-derived molecules and all possible reactions from biomass-derived molecules. In this optimization problem, the main constraint for the reaction is its thermodynamic favorability within a certain temperature range. Using optimization solver, optimal solutions for this problem are obtained. Using this developed approach, a case study on upgrading fast-hydropyrolysis vapor of cellulose to higher molecular weight products was investigated. Levoglucosan and glycolaldehyde are major components from fast-hydropyrolysis of cellulose. This approach identified a reaction route that can upgrade these molecules to hydrocarbons with carbon number ranging from eight to 12 and this route has not been reported in the literature. The coupling of levoglucosan and glycolaldehyde requires a key intermediate, levoglucosenone, which is identified by this approach. Preliminary experimental results suggest that the proposed reactions are feasible and this serves as another validation for this approach. Other potential pathways to not only branched alkanes, but also substituted cycloalkanes and aromatics, were also identified. Molecules with those structures have been observed experimentally, and potential pathways to those molecules can provide insights for experimentalists as to how these products can form and which intermediates may lead to their formations. This approach has not only revealed unknown reaction routes, but also provided insights for experimentalists for analyzing complex systems.

Degree

Ph.D.

Advisors

Agrawal, Purdue University.

Subject Area

Alternative Energy|Chemical engineering|Petroleum engineering

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